ZooKeeper Tutorial

What is ZooKeeper?

ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services in distributed applications. It is a crucial component in distributed systems, often used in conjunction with Apache Kafka for managing its brokers and topics.

Core Concepts

ZooKeeper is built on a data structure called a Znode. Znodes can be thought of as nodes in a tree structure where each node can store data. The key concepts include:

• Znodes: These are the nodes in the ZooKeeper data structure. Each znode can hold data and has a unique path.
• Sessions: ZooKeeper clients interact with the service through sessions. Each session is identified by a unique session ID.
• Watches: Clients can set watches on znodes to get notifications of changes.
• Quorum: ZooKeeper uses a quorum-based approach to ensure consistency across distributed environments.

Installing ZooKeeper

To install ZooKeeper, follow these steps:

1. Download the latest version of ZooKeeper from the Apache ZooKeeper releases page.
2. Extract the downloaded tar file:
tar -xzf zookeeper-.tar.gz
3. Navigate to the extracted directory:
cd zookeeper-
4. Create a configuration file:
cp conf/zoo_sample.cfg conf/zoo.cfg
5. Edit conf/zoo.cfg to configure your ZooKeeper instance.

Starting ZooKeeper

To start ZooKeeper, run the following command:

To check the status of your ZooKeeper server, use:

Using ZooKeeper with Kafka

ZooKeeper is used by Kafka to manage brokers and topics. When you start a Kafka broker, it registers itself with ZooKeeper. Here’s how to configure Kafka with ZooKeeper:

1. In the server.properties file of your Kafka installation, set the following properties:

zookeeper.connect=localhost:2181

broker.id=0

listeners=PLAINTEXT://localhost:9092

2. Start the Kafka server:
bin/kafka-server-start.sh config/server.properties

ZooKeeper CLI

ZooKeeper provides a command-line interface (CLI) for managing znodes. You can start the CLI using:

Once in the CLI, you can perform various operations:

• Create a znode:
  create /myZnode myData
• List znodes:
  ls /
• Get data from a znode:
  get /myZnode
• Delete a znode:
  delete /myZnode

Conclusion

ZooKeeper is a powerful tool for coordinating distributed applications. Its ability to manage configuration, naming, synchronization, and group services makes it an essential component in many distributed systems, including Apache Kafka. Understanding how to install, configure, and use ZooKeeper can significantly enhance the reliability and performance of your distributed applications.